10:15 〜 10:30
[PPS03-11] リュウグウサンプル中の有機物の記載とその形成過程の解明
キーワード：はやぶさ２、リュウグウ、有機物
Hayabusa2 spacecraft succeeded to acquire particles from the surface and/or subsurface of the C-type asteroid Ryugu, through acquisition processes with considerably small effect of the contamination during and/or after the sampling. The particles were sealed in a vacuumed condition after the sampling on the asteroid, and directly installed into the clean chamber of the Japan Aerospace Exploration Agency, Extraterrestrial Sample Curation Center (ESCuC/JAXA) which is filled with pure nitrogen, to minimize terrestrial contamination [1].
Samples provided to the Phase2 Curation Kochi team were separately processed, with particles larger than 1mm and smaller particles less than 100 µm. Larger particles were analyzed by integrated bulk chemical analysis that starts from non-destructive analysis, such as synchrotron radiation experiments, to destructive analysis such as Laser-assisted IRMS for high precision O isotope analysis [2], bulk major and trace elemental abundances by INAA[3], mineralogy-petrology observations by FE-SEM and EPMA[4], crystallographic study by XRD[5], as well as O and C isotopic analysis with in-situ SIMS analysis[6][7]. Along with these analyses, we conducted a coordinated sequential micro-analysis for small particles around 100 µm which were separated from the larger particles for organic materials without X-ray irradiation during the synchrotron radiation experiments [8][9][10].
In-situ observation by scanning transmitted x-ray microscope with near edge x-ray absorption fine structure (STXM-NEXAFS) provides not only nano-scale texture of organic materials based on their molecular structures but also petrographic relationship with the surrounding minerals [e.g. 11]. Ultrathin sections of small Ryugu samples of C0009, C0068, A0002 and A0037, were picked up by FIB, and fixed on devices specially developed for the sequential analysis of organic matters [12].
C K-edge NEXAFS analysis of Ryugu samples shows strong peak of hydrocarbons at around 287.5 eV. The feature is different from previous studies of C K-edge NEXAFS analysis of any other carbonaceous chondrites. Portions enriched in hydrocarbon show strong correlation with grains with feathery textures. TEM analysis confirmed that the grains consist of intergrowth of serpentine and saponite, called as a coarse-grained phyllosilicate [e.g. 13]. The close correlation suggests that hydrocarbon species were formed by aqueous alterations, through an interaction between carbonaceous and silicate materials.
References
[1] Yada et al. (2021) Nat. Astron. https://doi.org/10.1038/s41550-021-01550-6, [2] R. C. Greenwood et al., (2022) 53rd LPSC [#2105], [3] Shirai et al., (2022) JPGU, [4] Yamaguchi et al. (2022) 53rd LPSC. [#1822], [5] Imae et al., (2022) JPGU, [6] Liu et al. (2022) 53rd LPSC. [#2276], [7] McCain/Matsuda et al. (2022) 53rd LPSC. [#2432], [8] Ito et al. (2022) 53rd LPSC. [#1601], [9] Tomioka et al. (2022) 53rd LPSC. [#1710], [10] Ito et al. (2022) Nature Astronomy, submitted., [11] Le Guillou et al. (2014) Geochim. Cosmochim. Acta, 131, 368–392, [12] Ito et al. (2020) Earth Planet Space, 72:133 [13] Tomeoka and Buseck (1988) Geochim. Cosmochim. Acta, 52,1627-1640
Samples provided to the Phase2 Curation Kochi team were separately processed, with particles larger than 1mm and smaller particles less than 100 µm. Larger particles were analyzed by integrated bulk chemical analysis that starts from non-destructive analysis, such as synchrotron radiation experiments, to destructive analysis such as Laser-assisted IRMS for high precision O isotope analysis [2], bulk major and trace elemental abundances by INAA[3], mineralogy-petrology observations by FE-SEM and EPMA[4], crystallographic study by XRD[5], as well as O and C isotopic analysis with in-situ SIMS analysis[6][7]. Along with these analyses, we conducted a coordinated sequential micro-analysis for small particles around 100 µm which were separated from the larger particles for organic materials without X-ray irradiation during the synchrotron radiation experiments [8][9][10].
In-situ observation by scanning transmitted x-ray microscope with near edge x-ray absorption fine structure (STXM-NEXAFS) provides not only nano-scale texture of organic materials based on their molecular structures but also petrographic relationship with the surrounding minerals [e.g. 11]. Ultrathin sections of small Ryugu samples of C0009, C0068, A0002 and A0037, were picked up by FIB, and fixed on devices specially developed for the sequential analysis of organic matters [12].
C K-edge NEXAFS analysis of Ryugu samples shows strong peak of hydrocarbons at around 287.5 eV. The feature is different from previous studies of C K-edge NEXAFS analysis of any other carbonaceous chondrites. Portions enriched in hydrocarbon show strong correlation with grains with feathery textures. TEM analysis confirmed that the grains consist of intergrowth of serpentine and saponite, called as a coarse-grained phyllosilicate [e.g. 13]. The close correlation suggests that hydrocarbon species were formed by aqueous alterations, through an interaction between carbonaceous and silicate materials.
References
[1] Yada et al. (2021) Nat. Astron. https://doi.org/10.1038/s41550-021-01550-6, [2] R. C. Greenwood et al., (2022) 53rd LPSC [#2105], [3] Shirai et al., (2022) JPGU, [4] Yamaguchi et al. (2022) 53rd LPSC. [#1822], [5] Imae et al., (2022) JPGU, [6] Liu et al. (2022) 53rd LPSC. [#2276], [7] McCain/Matsuda et al. (2022) 53rd LPSC. [#2432], [8] Ito et al. (2022) 53rd LPSC. [#1601], [9] Tomioka et al. (2022) 53rd LPSC. [#1710], [10] Ito et al. (2022) Nature Astronomy, submitted., [11] Le Guillou et al. (2014) Geochim. Cosmochim. Acta, 131, 368–392, [12] Ito et al. (2020) Earth Planet Space, 72:133 [13] Tomeoka and Buseck (1988) Geochim. Cosmochim. Acta, 52,1627-1640